feat: support ability to retrieve individual metadata types and/or items

[techfg]

The retrieve command will retrieve an entire workspace, however there are use cases where only a portion of a workspace requires retrieval.

For example, when working on a component pack, if you are simultaneously using the Web UI Builder to design views, etc. and working in an IDE to develop code, you need to be very diligent about managing retrieve and deploy commands from the CLI to ensure that you don't "lose/destroy" something you did in the Web UI when deploying or something local in code when retrieveing.

The retrieve command should allow for specifying what meta data type(s) and/or item(s) should be retrieved. This will improve overall administration of a workspace and also greatly improve the developer experience.

Note

Currently, when "retrieving", the entire bundle directory is deleted and replaced with the retrieved files. In the case of "partial" retrieve, this would result in only the retrieved files existing and not everything else so changes will need to be made to ensure that only the files being changed are deleted. It should possibly be considered that "retrieve" in general not delete anything local as the default behavior and only delete when a flag like --clean is specified.

Related #4389, #4408